Estrogens refer to a group of hormones that play a number of well known roles in the body, including tissue and bone maintenance. Estradiol is the principal intracellular human estrogen, and is found in both women and men. Estrogen has its effect through binding of the estrogen receptor (“ER”). In endothelial cells, 17β-estradiol (E2) inhibits IL-1β induced NF-κB reporter activity and IL-6 expression in an ER dependent fashion (Kurebayashi S. et. al., J. Steroid Biochem. Molec. Biol., 1997, 60, 11). This correlates with anti-inflammatory action of E2 in vivo as confirmed in different animal models of inflammation. In models of atherosclerosis, E2 was shown to protect endothelial cell integrity and function and to reduce leukocyte adhesion and intimal accumulation (Adams, M. R. et al., Arterio., 1990, 1051, Sullivan, T. R. et al. J. Clin. Invst., 1995, 96, 2482, Nathan, L. et. al., Circ. Res., 1999, 85, 377). Similar effects of estrogen on the vascular wall have also been demonstrated in animal models of myocardial infarction (Delyani, J. A. et al., J. Molec. Cell. Cardiol., 1996, 28, 1001) and congestive heart failure. Clinically, estrogen replacement therapy (ERT) has been demonstrated to reduce the risk of mortality in patients with both CHF (Reis et. al., J. Am. Coll. Cardio., 2000, 36, 529) and MI (Grodstein, F. et. al., Ann. Int. Med., 2000, 133, 933, Alexander et. al., J. Am. Coll. Cardio., 2001, 38, 1 and Grodstein F. et. al., Ann. Int. Med, 2001, 135, 1). In ERT, clinical studies demonstrated an influence of E2 on the decrease in the production of β-amyloid 1-42 (Aβ42), a peptide central for the formation of senile plaques in Alzheimer's disease (Schonknecht, P. et. al., Neurosci. Lett., 2001, 307, 122).
Until recently, estrogen replacement therapy was thought to be highly desirable for preventing a host of disorders, including inflammation, osteoporosis, and heart disease. However, 17-β-estradiol also strongly stimulates creatine kinase expression. Thus, in ERT some potential unwanted side effects, such as an increase risk of cardiovascular events in the first year of use, have been demonstrated (Hulley, S. et. al., J. Am. Med. Assoc., 1998, 280, 605) as well as proliferative effects on uterine and breast tissue.
Therefore, ligands for the estrogen receptor are highly sought after, in order to provide the benefits noted with supplying estrogen, but without the associated risks. Estrogen receptor ligands are useful for the treatment of the inflammatory component of diseases and are particularly useful in treating atherosclerosis, myocardial infarction, congestive heart failure, inflammatory bowel disease, arthritis, type II diabetes, and autoimmune diseases such as multiple sclerosis and rheumatoid arthritis. The ability of ligands for the estrogen receptor to inhibit inflammatory gene expression causing a reduction of cytokines, chemokines, adhesion molecules and inflammatory enzymes provides a means to treat the inflammatory component of diseases such as atherosclerosis, myocardial infarction (MI), congestive heart failure (CHF), inflammatory bowel disease and arthritis. Other potential therapeutic indications for these type of molecules include type II diabetes (Cefalu, J Womens Health & Gender-based Med., 2001, 10, 241 & Yuan et al., Science, 2001, 293, 1673), osteoarthritis (Pelletier et al., Arthr. & Rheum., 2001, 44:1237 and Felson et al., Curr Opinion Rheum, 1998, 10, 269) asthma (Chin-Chi Lin et. al., Immunol. Lett., 2000, 73, 57), Alzheimer's disease (Roth, A. et. al., J. Neurosci. Res., 1999, 57, 399) and autoimmune diseases such as multiple sclerosis and rheumatoid arthritis.
A common component of these chronic inflammatory conditions is polymorphonuclear leukocyte and monocyte infiltration into the site of damage through increased expression of cytokines and adhesion molecules responsible for their recruitment. Overproduction of the cytokine interleukin (IL-6) has been associated with states of chronic inflammation (Bauer M. A., Herrmann F., Ann. Hematol., 1991, 62, 203). Synthesis of the IL-6 gene is induced by the transcription factor, nuclear factor κB (NF-κB). Interference at this step in the inflammatory process can effectively regulate the uncontrolled proliferative process that occurs in these chronic conditions.
Thus, ER ligands are highly desirable for treating inflammation, and developing new ER ligands is an important undertaking.